Greenhouse propagation of the endangered hemiparasiteSchwalbea americana(American chaffseed): experimentation and botanical studies

Abstract

American chaffseed ( Schwalbea americana L. [Scrophulariaceae]) is a federally endangered, hemiparasitic species that primarily occurs in fire-maintained pinelands in the Atlantic and Gulf coastal plains of the US. Efforts to propagate S. americana for re -introduction into the wild have been met with mixed results. Discrepancies in our understanding of host requirements, soil ecology, and growing conditions need to be resolved in order to develop a successful ex situ propagation program. We conducted a series of greenhouse experiments to address the impact that growth media, soil microbes, mycorrhizal associations, and autoparasitism may have on successful propagation of seedlings. We also tested the effectiveness of storing bareroot plants at 4°C (39 °F) relative to plants overwintering outside or being maintained in the greenhouse. We confirmed that cold-moist stratification is necessary to achieve the high germination rates needed for ex situ propagation. Soil microbes and growth media affected S. americana survivorship. We successfully grew plants in the absence of host plants by supplementing nursery media with organic hydrolized fish fertilizer. We did not observe S. americana forming mycorrhizal associations or parasitizing its own roots (no autoparasitism). Finally, we demonstrated that 1-y-old bareroot plants stored for 3 mo at 4°C exhibited survival rates that rivaled plants that overwinter outdoors or in the greenhouse.